disabling power on gpio pins during boot

Hey Everyone,

I’m a n00b so please excuse me, but I have been trying to get my BBB to boot with no power on P9-pin 11.

Controlling them through /sys/class/export works fine but even if I write a bash script to disable power, it still stays on for about 5 seconds before my script runs to cut power.

So, obviously I learned bash scripts are not the way to go here.

Next, I tried exploring making the config changes in the boot loader. I’ve modified beagle.c in u-boot source and commented out this entire section:

/* Set GPIO states before they are made outputs
writel(GPIO23 | GPIO10 | GPIO8 | GPIO2 | GPIO1,
writel(GPIO31 | GPIO29 | GPIO28 | GPIO22 | GPIO21 |
GPIO15 | GPIO14 | GPIO13 | GPIO12, &gpio5_base->setdataout); */

/* Configure GPIOs to output
writel(~(GPIO23 | GPIO10 | GPIO8 | GPIO2 | GPIO1), &gpio6_base->oe);
writel(~(GPIO31 | GPIO29 | GPIO28 | GPIO22 | GPIO21 |
GPIO15 | GPIO14 | GPIO13 | GPIO12), &gpio5_base->oe); */

Recompiled, put MLO and u-boot.img in my /boot/uboot path but it still doesn’t seem to work.

Again, I apologize for the n00bness, but would someone that has experience doing this kind of thing be able to at least point me in the right direction?

are there other methods I can use in this $gpio5_base?

End goal is to be able to hook up my multimeter to pin 11 on P9, boot the device and never see voltage, until I want it (I got that part down)

Did you fix this problem?
Because I m facing the same undesired behavior.


Only way to do this is to isolate the pins with a gate, enable the gate
with a signal of your choice that you can turn on after your no power
period is over